1. Field of the Invention
The present invention relates to an ejection surface cleaning apparatus, a liquid ejection apparatus and an ejection surface cleaning method, and more particularly, to technology for maintaining the liquid ejection surface of a liquid ejection head.
2. Description of the Related Art
In general, an inkjet recording apparatus which forms a desired image by ejecting ink droplets from an inkjet head onto a recording medium is widely used as a generic image forming apparatus.
An inkjet recording apparatus is able to record images of high resolution and high quality at relatively low cost and at high speed, and therefore such apparatuses are employed widely from recording onto small or medium-sized papers aimed at individual use, to recording onto large-sized papers, such as posters intended for outdoor display. For example, when recording onto large-size paper intended for outdoor display, aqueous pigment-based inks having light resistant properties are generally used.
In an inkjet recording apparatus, ink is liable to adhere to the ink ejection surface (nozzle surface) of the inkjet head, and if residual ink of this kind solidifies, then it can cause ejection abnormalities, such as abnormalities in the ink ejection volume or abnormalities in the ejection direction. In particular, with aqueous pigment-based ink, aggregation is liable to occur if the conditions are such that drying of the ink proceeds very rapidly, thus causing the ink adhering to the nozzle surface to solidify and leading to blocking of the nozzles and decline in printing quality. Consequently, it is necessary to carry out periodic maintenance (cleaning) of the ink ejection surface of the inkjet head.
Therefore, in order to resolve the problems described above, Japanese Patent Application Publication No. 2007-331166, for example, describes an inkjet recording apparatus according to which ink ejected from nozzles is recovered, the recovered waste ink is sprayed from a spray unit onto an ink ejection surface, and the ink ejection surface is wiped by a wiper. Furthermore, Japanese Patent Application Publication No. 2005-144737 describes an inkjet recording apparatus which sprays a cleaning liquid that dissolves or redisperses the ink, onto an ejection surface, wipes the ejection surface with a blade, and then suctions the ink via ejection holes.
However, in these apparatuses, if an aqueous pigment-based ink as described above is used, for example, then the ink is liable to dry and therefore cannot be removed adequately, and the remaining aggregated ink adheres again to the nozzles and the periphery of the nozzles, thus causing the print quality to decline. Moreover, since the state of the ink ejection surface changes each time an operation of wiping away the residual ink is carried out, then it is difficult to apply correction.
On the other hand, in order to remove solidified ink left adhering to a wiper blade in a reliable fashion, Japanese Patent Application Publication No. 2001-54949 describes an inkjet recording apparatus comprising a solution spraying device which sprays a solution capable of dissolving ink onto a wiping member, a leave time counting device which counts the leave time of the wiping member, and a wiping control device which controls a solution wiping operation by the solution spraying device.
However, if the wiping member cleaning technology described in Japanese Patent Application Publication No. 2001-54949 is applied to the cleaning of the ejection surface in order to remove solidified ink left adhering to the ink ejection surface of the inkjet recording apparatus described in Japanese Patent Application Publication No. 2007-331166 and Japanese Patent Application Publication No. 2005-144737, then since the leave time during which the cleaning liquid (solution) deposited onto the ink ejection surface is left on the ink ejection surface is a fixed time, problems of the following kind arise. More specifically, if the leave time of the cleaning liquid is set too short, then the ink adhering to the ink ejection surface is not wiped away sufficiently, and this gives rise to decline in printing quality. On the other hand, if the leave time of the cleaning liquid is too long, then time is spent unnecessarily on the maintenance operation and this give rise to decline in productivity. Furthermore, if the leave time of the washing liquid is set too long, then under high-temperature and low-humidity conditions, the cleaning liquid itself may dry out, and there is a possibility that a hard film may form over the whole of the ink ejection surface.